Conventionally, there is known a vehicle brake device for detecting the pressure of a master cylinder which is varied in response to the brake operation amount of a driver by a detection means such as a pressure sensor and the like and controlling the lighting state of a brake lamp and controlling the brakes of respective wheels based on the detected master cylinder pressure.
In general, in the sensors such as the pressure sensor and the like, since a sensor output value corresponding to a zero-point is varied by a secular variation such as a temperature drift and the like and an aged deterioration, a phenomenon may occur in that a sensor output value is not zero regardless that an actual pressure is zero, i.e. a so-called zero-point offset.
In the vehicle brake device, to accurately control the turn-on of a brake lamp and the brakes of respective wheels, it is necessary to overcome the influence of the zero-point offset of the pressure sensor. Accordingly, the master cylinder pressure is calculated by excluding the influence of the zero-point offset by correcting the output value of the pressure sensor based on an optional zero-point correction value.
The zero-point offset amount of the pressure sensor may be varied by the secular variation and the aged deterioration as described above, it is necessary to appropriately update also the zero-point correction value of the pressure sensor. For example, Patent Literature 1 discloses a technology for determining, when a stop lamp switch is turned off (when a brake lamp is not lit), no brake operation is executed, that is, a brake pedal is not depressed and an intrinsic master cylinder pressure must be 0 and updating the zero-point correction value of a pressure sensor at the timing.